The effects of electron viscosity and parallel flow on resonant layer responses to 3D magnetic perturbations

Non-axisymmetric magnetic perturbations arising in a tokamak can induce complex plasma responses near the resonant surface. In this region, the plasma will no longer adhere to ideal MHD and will instead demand the reconnection of magnetic field lines which can grow and significantly alter the plasma profile. The resonant layer response can be characterized completely in a linear regime by a single parameter called the inner-layer Δ [1]. Here we apply a two-fluid drift-MHD model to identify the scaling of Δ in various asymptotic regimes while investigating additional effects including electron viscosity and parallel flow and confirm the predictions using a numerical method based on the Riccati transformation [2]. We identify regimes in which these additional effects have a significant impact on Δ, as this will in turn alter the field penetration threshold which is important in MHD stability. These Δ calculations have also been used to predict the field penetration threshold by matching to outer-layer response solutions in general perturbed equilibrium code (GPEC), and validate the predictions over the tokamak error field database. [1] R. Fitzpatrick, Phys. Plasmas 29, 032507 (2022) [2] J.-K. Park, Phys. Plasmas 29, 072506 (2022)